Who has an AR pistol / SBR?

Either that or an AR SBR, and hows it running? Im getting ready to build my upper reciever to run as a pistol until my SBR stamp comes in.

Im having a hard time deciding between a 7" or 10" barrel. I really want a 7" barrel but am wondering about operating issues with the shortened dwell time of the 7" barrel. Seems like people are having problems with short stroking due to the limited time of gas redirect.

So, who has what and how does it run? Or better yet, whos ever built their one 7" or 10" uppers and how do they run? Anything I need to be aware of before I bolt this thing together?

A very close friend of mine picked up a used 7" (or 7.50") complete upper about a year ago.
It's a Model 1 Sales. Model 1 gets a big BOO HISSS from a lot of folks (I wouldn't give you $0.02 for their LPK's)
But.... It has run like a sewing machine since day one. We've put at least 3,000/rnds through it.
However, we haven't shot any junk ammo through it. It's had nothing but S&B down the pipe.
It's kind of a toy for him, but it's a bad-*** little piece of hardware.

I would think that having the correct spring & buffer is the key to making one run correctly. That's going on the basis that the upper is all "okay" to begin with.

I have a kel tec; 100% reliable with all ammo. Uses a forward moving, and then recoil piston/op rod setup. Also accurate, and you can attach all your normal ar stuff on it, and it uses ar mags.
It will also be the loudest thing you have ever shot. I think it is a 10 inch bbl.

My 10 1/2" Model 1 has had no issues(no issues running that is). I wouldn't go any shorter than that mostly out of fear of muzzle flash, percussion, and lord forbid if (for whatever reason) you had to use it as a defensive tool, I would want some velocity. Lastly I've really only heard of issues runnng barrels shorter than 10-11", or guys running those really short pistol buffers, I just used a CAR buffer tube, and like I said, haven't had a problem yet.

Most of the complaints of Model 1 are of fit, finish, possibly missing parts, or non spec parts. My 10 1/2" kit was missing the buffer retainer, and the gas key was not properly staked. I had to re-tighten it my self. Oh, and my lower was a little tight, or the part was out of spec, and I had to shave down the front pivot pun retaining detent. I think it's the lower, because Pro Mag 20's won't drop free of it, but do in my Bushmaster. If you can get past that, they will run, believe it or not(lol).

I hope to SBR my pistol someday, but the whole sign-off thing has slowed down the process. Nobody will sign around here, so now I'm looking into living trusts.

I personally would stay above 10" for two reasons. First, so I could run a suppressor on it with out fear of baffle or end cap strikes. Second, going from a 10.5" barrel to a 7" barrel the velocity loss seems to outweigh the reduction in length. That's just me though and is of course influenced by how I use my guns.

Because of the reasons above my preference for a SBR is something in pistol caliber. My suggestion would be a 9mm or .45 AR upper and build your SBR from that.
9mm fired from a short barrels have put down plenty of bad guys. Just sayin'.

You really want an 11.5" barrel. Significantly more reliable - you're talking about nearly a 100% increase in barrel length past the gas port (and thus an increase in dwell time of the impulse to cycle the gun) versus a 10.5". Add to that a lower flash, less noise, and higher velocity, and it's all around the best choice while still being quite small.

That's not an issue if you never intend to use the gun for serious purposes.

Because of the reasons above my preference for a SBR is something in pistol caliber. My suggestion would be a 9mm or .45 AR upper and build your SBR from that.
9mm fired from a short barrels have put down plenty of bad guys. Just sayin'.

Click to expand...

9mm AR plus a suppressor equals lots of crud in the face.

Further my chrono has a 115 gr. 9mm out of a 16" barrel going aprox 1500 FPS. It is picking up about 200 FPS over a full size handgun. Its like a .357 sig.

A 10.5" 5.56 is going to be doing roughly 2600 FPS with a 55 grain bullet or 2400 with a 75 grain round. (I'd need to check those numbers to be precise but they shouldn't be too far off)

A 9mm SBR is not on par with a 5.56 SBR.

If you are really worried about put down a 6.8 SPC can send a 110 grain pill at 2700 FPS or so from a 10" barrel. And a .458 socom hardly loses anything in SBR form from what I've seen.

I have a factory 10.5 form M1s that runs great. The big thing with Sbrs is having proper gas port size all my 7.5 /10.5 /10.5 and 14.5 uppers have .93 gas ports. I have had to stick a few uppers int he mill and open the gas port up because soem places still use .83 or .86 as their spec for 11.5s ( cant rember which it is).

Just a hair under 9" seems to be the magic number for 5.56mm. Velocity is lost relatively slowly until about 8.75"... then it falls like a rock. 10.5" gun, 5.56 all the way, I love mine, and if I ever had to go back into harm's way, it would be going with me. If you want super, super short (7" or below), 9mm is a better bet... easier to make run (no gas system in a 9mm), much heavier bullets (5.56 isn't going much faster than +P 9mm with a 7" barrel), and cheaper practice ammo.

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